Effect Of Large-scalelinear Engineering Projects On Vegetation Fractions In Alpine Shrubland

As an important ecological factors, vegetation is used to monitor the ecological environment and climate change.Vegetation fraction, which is an important indicator to characterizevegetation, is always served as the important parameter and basic datum in global or regional hydrological ecology research. Transportation construction projects is a kind of typical large-scale linear engineering, and characterized by long construction period, large excavation disturbance, etc.Golmud to Lhasa of Qinghai-tibet railway is located in the hinterland of Qinghai-tibet plateau, the railway construction has caused the inevitable disturbance to the ecological environment around the railway during the process of excavation and vegetation removal.Therefore, estimating the vegetation fraction along Qinghai-tibet railway and analyzing its influence change has an important scientific significance for strengthening the protection of the surrounding ecological environment along the railway and the corresponding prevention measures.In this thesis,Damxung section of the Qinghai-tibet railway is selected as the study area. First,two Landsat remote sensing data acquired in 1994 and 2014 were selected as the research data, and the vegetation classification was confirmed and completed based on detailed precision comparisons among the methods of maximum likelihood, spectral mixture analysis, spectral Angle mapping and support vector machine(SVM). Thenvegetation fraction estimation was conducted using the normalized difference vegetation index method. Finally, the study area was divided into 12 buffer zones, and the vegetation fractionin each buffer zone was calculated. The vegetation fraction differences between the adjacent buffer zones were also analyzed vegetation fraction difference changes. The main conclusions were drawn as the following.(1) Total vegetation fraction: Within the scope of the northern railway 1 km and 10 kilometers south railway,the vegetation fractionbetween adjacent areas is large different. It shows that the railway caused impact on vegetation.The distance closer, the vegetation fraction decreased greater;(2) Stipa purpurea in the south of the railway 30 kilometers; Rhododendron nivalein the north of line two kilometers, 30 kilometers south; Kobresia pygmaea within two kilometers north of railway, vegetation fraction difference between adjacent areas were reduced, this suggests that the farther away from the railway, the smaller the vegetation fraction;(3) Sabina pingii var wilsonii in the north of line 1 km, 20 km south; Kobresia littledaleiin the north of railway 1 km, south within 10 km; Kobresia pygmaea within two kilometers down the railway line, vegetation fraction difference between adjacent areas were bigger, this suggests that railway operation makes impact on vegetation, the nearer the railway line, the greater the impact;(4) The railway in the north due to the influence of many factors(such as human activity, mountain distribution, precipitation, etc), the regularities of the variation influenced by pure railway is not obvious, because of less affected in the south, railway’s influence regularities on the variation of the vegetation fraction is clear and consistent.